Compressed gas circuit breaker

ABSTRACT

A compressed gas circuit breaker is disclosed having a closed gas circuit, in which an electro-negative gas (preferably sulphur hexafluoride) serves as the quenching medium to quench any electrical arc formed between two electrical contacts upon the operation of the breaker. In the device the gas flows from a high-pressure tank where the gas is stored into a low-pressure space containing a quenching chamber where the electrical contacts are located. The flow occurs upon the opening of a blast valve connecting the high-pressure tank with the low pressure space and the quenching chamber. The high pressure is obtained by means of two pressure producing devices. The first is a compressor which, after the operation of the breaker, returns the gas from the low-pressure space to the high-pressure tank and raises the pressure of the gas to a pressure lower than the liquefaction pressure of the gas at low operating temperatures. The gas is thereupon stored in the high-pressure tank under these conditions until the breaker operates again. The high-pressure tank further contains a second gas compression means by which the gas pressure is further increased to a higher pressure at the time it is supplied to the quenching chamber or low-pressure space when the electrical arc is formed by the operation of the circuit breaker.

United States Patent [191 Muller et al.

[111 3,806,681 51 Apr. 23, 1974 COMPRESSED GAS CIRCUIT BREAKER [75] Inventors: Hans-Georg Muller, Essen; Heinrich Busch, Wesel, both of Germany [731' Assignee: Siemens Aktiengesellschaft, Munich,

Germany [22] Filed: May 26, 1972 [2]] Appl. No.: 257,162

[30] Foreign Application Priority Data May 28, 1971 Germany P 21 27 494.2

[52] US. Cl. 200/148 E, 200/148 A [51] Int. Cl. H0111 33/57 [58] Field of Search 200/148 E, 148 A, 148 B, 200/148 R [56] References Cited UNITED STATES PATENTS 3,622,725 11/1971 McConnell 200/148 E 3,662,135 5/1972 Clark 200/148 R Primary Examiner-Robert S. Macon Attorney, Agent, or Firml(enyon & Kenyon Reilly Carr & Chapin [57] ABSTRACT A compressed gas circuit breaker is disclosed having a INSULA TOR closed gas circuit, in which an electro-negative gas (preferably sulphur hexafluoride) serves as the quenching medium to quench any electrical are formed between two electrical contacts upon the operation of the breaker. In the device the gas flows from a high-pressure tank where the gas is stored into a low-pressure space containing a quenching chamber where the electrical contacts are located. The flow occurs upon the opening of a blast valve connecting the high-pressure tank with the low pressure space and the quenching chamber. The high pressure is obtained by means of two pressure producing devices. The first is a compressor which, after the operation of the breaker, returns the gas from the low-pressure space to the high-pressure tank and raises the pressure of the gas to a pressure lower than the liquefaction pressure of the gas at low operating temperaturesThe gas is thereupon stored in the high-pressure tank under these conditions until the breaker operates again. The high-pressure tank further contains a second gas compression means by which the gas pressure is further increased to a higher pressure at the time it is supplied to the quenching chamber or low-pressure space when I the electrical arc is formed by the operation of the circuit breaker.

9 Claims, 1 Drawing Figure VA urn/mum 2 33 ACLUMl/MTOR 1 COMPRESSED GAS CIRCUIT BREAKER FIELD OF THE INVENTION BACKGROUND OF THE INVENTION In compressed gas circuit breakers, the quenching gas flows from a high-pressure tank into a low-pressure space upon the opening of a blast valve. Such circuit breakers usually use. sulphur hexafluoride as the quenching and insulating medium. These breakers, known as dual-pressure gas circuit breakers, after operating, recycle the gas to the high-pressure tank or space to maintain a definite pressure difference between the high-pressure tank and the low-pressure space. Up to now, the pressure difference had to be very large in order to produce a gas flow suitable for the quenching of the electrical are formed upon operation of the breaker. Because the low pressure of the gas in the circuit breaker is generally predetermined, and because the gas used as the insulating medium is required to have a certain minimum pressure to properly insulate, the pressure in the high-pressure tank in modern circuit breakers is to atmospheres or more. This pressure, which in itself is not very high and can be technically well handled, can, however, lead to difficulties at temperatures near zero degrees Centigrade where such electro-negative gases can cause condensation.

Alternatively, electro-negat ive gases previously have been used in so-called blast piston circuit breakers in which there is no closed gas circuit with a continuously maintained pressure difference. In this type of breaker the gas is maintained at a pressure of a few atmospheres so that the flow required for quenching the arc must be produced by means of a special pumping device which operates at the moment of switching. Up to the present, however, such blast piston breakers have been used only for small breaker ratings, because to obtain the pressure difference used to quench the are caused by large currents (for example in dual-pressure gas breakers) would require excessively large pump installations, and more importantly, excessive operating power for blast-piston breakers.

It is therefore an object of the present invention to overcome these shortcomings of the prior art.

SUMMARY OF THE INVENTION Surprisingly, it has been, found that the disadvantages of the two types of compressed-gas breakers described above can be overcome; in accordance with this invention, by'providing the high-pressure tank with a gas at a pressure lower than the liquefaction pressure of the gas at low operating temperatures, and providing a blast piston by which the gas pressure is increased in a known manner at the instant the circuit breaker switches off.

The circuit breaker, according to the invention, is a dual-pressure breaker. Its high pressure, however, is lower than that which normally would be required in such circuit breakers to maintain a pressure difference suitable for quenching an electrical arc formed by the operation of the breaker. At very low operating temperatures a slight amount of heating possibly may be required. This'can easily be installed and does not change the power requirements of the circuit breaker appreciably.

In the operation of the breaker at theinstant the breaker is switched off, a blast piston becomes effective as a supplemental pumping device. For this purpose, however, small amounts of driving power are sufficient because the blast piston is only required to create the pressure difference between the existing high pressure of the gas and the high pressure required to quench the arc.

The use of a compressor and a supplemental blast piston may seem to be a large expense. However, the blast piston can advantageously be operated hydraulically by means of an hydraulic accumular, which is commercially available at a reasonable cost. In comparison to the other known circuit breakers, not only is the expense for the heating system saved but additional savings are realized because the compressor is required only to generate a low pressure difference.

In the circuit breaker of this invention the drive for the blast piston is advantageously controlled by being coupled to the actuation of the blast valve. In other words, the blast piston can be operated only if the blast valve is open so that the blast piston can become immediately effective to provide gas to flow over the arc.

. In the preferred embodiment of the invention, the blast piston has a check valve and the compressor is connectedto that side of the cylinder associated with the blast pistonwhich faces away from the blast valve. By this combination, the blast piston only produces the 1 higher pressure necessary to quench the arc. Low pressures which would hinder the movement of the blast piston cannot, therefore, be developed.

- DESCRIPTION OF THE DRAWING FIG. 1 is a schematic representation of a circuit breaker constructed according to this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT In order to explain the invention in further detail, an

. example of apreferred embodiment will be described with reference to FIG. 1. In the drawing, only the quenching chamber with the essential components belonging to the dual-pressure, gas circuit breaker for high voltage, using sulphur hexafluoride as the quenching medium, are schematically shown in detail. The tubular insulators which insulate the quenching chamber from ground, and the other parts which connect the circuit breaker into a switching installation, are only shown in a simplified schematic manner.

The circuit breaker head 1, supported by a'tubular insulator 30, comprises a quenching chamber 2 formed of insulating material. One end face of the chamber is terminated in a metallic receiver 3. The other end face of the quenching chamber is mounted on a metallic drive housing 4. One of the line terminals is attached to the drive housing, while the other line terminal is attached at receiver 3. The tubular insulator 30 is mounted on a dolly 31 to permit the circuit breaker to be moved about within the station.

The circuit breaker head 1 includes a high-pressure tank for the sulphur hexafluoride. In the drawing of the preferred embodiment, this high-pressure tank is generically illustrated by cylinder 5 of the blast piston pump device 6. Within the pump device 6 an hydraulic actuator cylinder is connected to the blast cylinder 5. Within the actuator cylinder 10 an'hydraulic actuator piston 8 is connected to blast piston 7 mounted within blast cylinder 5. Control valves 32 and 33 connect the actuator cylinder 10 with an hydraulic accumulator 34 in which hydraulic medium is stored under pressure.

As will be seen, the blast piston 7 contains a check valve 12, which is normally open, and closes only during the pumping motion of the piston 7 when it moves from the top to the bottom of the blast cylinder 5. A blast valve 13 is mounted in the cylinder 5 beneath the blast piston 7 and opposite to the actuator 10. The blast valve 13 separates the blast cylinder 5, which serves as the high-pressure tank, from the quenching chamber 2. This chamber 2 is connected with the interior 14 of the drive housing 4 by a pipe 40. Together they constitute the lowpressure space or tank and contain the sulphur hexafluoride gas at a pressure, for example, of 2 atmospheres.

In the quenching chamber 2 a stationary hollow contact 15 is attached to the wall of the receiver 3. This contact 15 is connected-in the closed position of the breaker with a hollow, movable contact 16. A nozzle 17, formed of insulating material, is arranged between the contacts 15 and 16 and is connected with the blast valve 13 by a tube 18.

A drive rod 37 is movably held within the tubular insulator 30. This rod 37 is activated by a double-acting hydraulic system 38. The rod 37 acts on both the blast valve 13 and on a lever mechanism 36 which transforms the vertical motion of the drive rod 37 into horizontal motion which is in turn coupled by rod 39 to" the movable contact 16.

Compressor 20, driven by motor 35, is connectedto the drive housing 4. The lower pressure side of the compressor is connected to the low pressure storage area 14 while the high pressure side of the compressor leads through the connection 21'to the blast cylinder 5 on the side of the blast piston 7 facing away from the blast valve 13. The high pressure of the gas can be selected,-for example, at 8 atmospheres, so that the pressure difference produced by the compressor 20 is only 6 atmospheres. At 8 atmospheres, heating of the circuit breaker is normally not required, as long as the breaker is located inside buildings in which the temper.- ature does not go below -l0 Centigrade. The small pressure difference required has the further beneficial advantage that the compressor can be made simple without the danger of leaks.

To open the circuit breaker, 'the blast valve 13 is opened. By controlling the valves 32 and 33, the hydraulic actuator piston 8 within actuator cylinder 10 is simultaneously acted upon by the hydraulic accumulator. This thereupon causes the blast piston 7 to move sure difference of 14 atmospheres is then available for' blasting the electrical arc which occursbetween the stationary contact 15 and movable contact 16 during the switching off of the breaker. This pressure difference is adequate to quench the electrical arc occurring LII at the highest currents in such circuit breakers. It can thus be seen from this that the circuit breaker constructed according to this invention requires no heating and does not impair the power handling capacity of the breaker. This advantageous effect is obtained solely by the use of a known pumping arrangement in a new combination with a dual-pressure gas circuit breaker, the high pressure of the gas being chosen so low that no liquefaction of the gas is to be expected even at low operating temperatures.

In the foregoing, the invention has been described in reference to specific exemplary embodiments. It will be evident, however, that variations and modifications, as well as the substitution of equivalent constructions and arrangements for those shown for illustration, may be made without departing from the broader scope and spirit of the invention as set forth in the appended claims. The specification and drawings are accordingly to be regarded in an illustrative rather than in a restrictive sense.

What is claimed is:

l. A compressed gas circuit breaker for quenching an electrical arc formed between two electrical breaker contacts upon operation of the breaker, said breaker employing an electronegative gas as a quenching gas, and having a closed gas circuit comprising a high pressure gas tank,

a low pressure gas space having a quenching chamber contained therein for quenching the electrical are formed in the chamber between two electrical breaker contacts upon operation of the breaker,

a first gas compression means connected between the low pressure space and the high pressure tank to recycle the quenching gas from the low pressure space to the high pressure tank after operation of the breaker and to raise the pressure of the gas returned to the high pressure tank to a pressure below the liquefaction pressure of the gas at low operating temperatures,

a second gas compression means connected to the high pressure tank to further increase the pressure of the quenching gas in the high pressure tank prior to its use as a quenching gas during the operation of the breaker, and

' blast valve means, connected between the high pres 1 sure tank and the quenching'chamber of 'the low pressure space, for regulating the flow of high pressure quenching gas into the quenching chamber to quench the electrical are formed between the two electrical breaker contacts upon operation of the breaker.

2. Acompressed gas circuit breaker as in claim I further comprising control means adapted to sequentially control the operation of the; breaker, the operation of the second gas compression means to further increase the pressure of the quenching gas, and the operation of the blast valve means to permit the high pressure quenching gas to flow into the quenching chamber to quench any electrical arc formed by operation of the breaker.

3. A compressed gas circuit breaker as in claim 2 wherein the high pressure gas tank isa cylinder, the first gas compression means comprises a motor driven compressor, and said second gas compression means comprises the combination of a reciprocating blast piston mounted within the high pressure gas cylinder and adapted to increase the gas pressre within the cylinder by physically compressing the gas in the high pressure gas cylinder, the piston further having a check valve mounted thereon to permit gas flow through said piston when said piston is inoperative and to prevent gas flow through said piston during the compression of the gas.

4. A compressed gas circuit breaker as in claim 3 further comprising hydraulic means to reciprocally move the blast piston comprising an hydraulic accumulator, an actuator cylinder hydraulically connected to the accumulator, a reciprocally movable actuator piston mounted within the actuator cylinder and directly connected to the blast piston whereby movement of the actuator piston directly moves the blast piston, hydraulic control valves between the accumulator and the actuator cylinder to control the supply of hydraulic fluid to the actuator piston and thereby control the movement of the blast piston and the compression of the quenching gas in the high pressure tank.

5. A compressed gas circuit breaker as in claim 4 wherein the compressor is connected between the low pressure spaceiand the upper portion of the blast cylinder above the blast piston.

6. A compressed gas circuit breaker as in claim 5 wherein the electro-negative gas used as the quenching gas is sulphur hexafluoride.

7. A compressed gas circuit breaker as in claim 5 wherein the low pressure space further comprises a nozzle formed from insulating material located in juxtaposition to the movable electrical contact and interconnected to the blast valve by a conduit.

8. A compressed gas circuit breaker as in claim 5 wherein movement of the electrical contacts and the blast valve is conjunctively controlled by a double acting hydraulic system, connected directly to the blast valve and coupled to the movable contact.

9. A compressed gas circuit breaker for quenching an electrical arc formed between two electrical breaker contacts upon operation of the breaker, said breaker employing an electro-negative gas as a quenching medium comprising a circuit breaker head mounted on an insulated movable carriage, said head having a quenching chamber therein formed of insulating material, two electrical contacts mounted within said chamber and connected to the electrical circuit, one of said contacts being movable, a nozzle formed of insulatingmaterial in juxtaposition to the contacts,

a high pressure tank adapted to store the quenching gas at pressures below the liquefaction pressure of the gas at low temperatures,

a low pressure space within said head including the quenching chamber,

a compressor connected between the low pressure space and the high pressure tank to remove gas at low pressures from the low pressure space and introduce the gas at a higher pressure to the high pressure tank,

blast piston means movably mounted in the high pressure tank to compress the high pressure gas to a higher pressure upon operation of the breaker, the piston being operated hydraulically by a second cylinder having an hydraulic piston activated by fluid from an hydraulic accumular, and controlled to operate the blast piston only when the breaker operates, and

a blast valve mounted between the high pressure tank and the low pressure space to permit the passage of quenching gas from the high pressure tank to the quenching chamber only when the breaker has operated and the electrical contact is disconnected and the blast piston has compressed the gas to a higher pressure. 

1. A compressed gas circuit breaker for quenching an electrical arc formed between two electrical breaker contacts upon operation of the breaker, said breaker employing an electronegative gas as a quenching gas, and having a closed gas circuit comprising a high pressure gas tank, a low pressure gas space having a quenching chamber contained therein for quenching the electrical arc formed in the chamber between two electrical breaker contacts upon operation of the breaker, a first gas compression means connected between the low pressure space and the high pressure tank to recycle the quenching gas from the low pressure space to the high pressure tank after operation of the breaker and to raise the pressure of the gas returned to the high pressure tank to a pressure below the liquefaction pressure of the gas at low operating temperatures, a second gas compression means connected to the high pressure tank to further increase the pressure of the quenching gas in the high pressure tank prior to its use as a quenching gas during the operation of the breaker, and blast valve means, connected between the high pressure tank and the quenching chamber of the low pressure space, for regulating the flow of high pressure quenching gas into the quenching chamber to quench the electrical arc formed between the two electrical breaker contacts upon operation of the breaker.
 2. A compressed gas circuit breaker as in claim 1 further comprising control means adapted to sequentially control the operation of the breaker, the operation of the second gas compression means to further increase the pressure of the quenching gas, and the operation of the blast valve means to permit the high pressure quenching gas to flow into the quenching chamber to quench any electrical arc formed by operation of the breaker.
 3. A compressed gas circuit breaker as in claim 2 wherein the high pressure gas tank is a cylinder, the first gas compression means comprises a motor driven compressor, and said second gas compression means comprises the combination of a reciprocating blast piston mounted within the high pressure gas cylinder and adapted to increase the gas pressre within the cylinder by physically compressing the gas in the high pressure gas cylinder, the piston further having a check valve mounted thereon to permit gas flow through said piston when said piston is inoperative and to prevent gas flow through said piston during the compression of the gas.
 4. A compressed gas circuit breaker as in claim 3 further comprising hydraulic means to reciprocally move the blast piston comprising an hydraulic accumulator, an actuator cylinder hydraulically connected to the accumulator, a reciprocally movable actuator piston mounted within the actuator cylinder and directly connected to the blast piston whereby movement of the actuator piston directly moves the blast piston, hydraulic control valves between the accumulator and the actuator cylinder to control the supply of hydraulic fluid to the actuator piston and thereby control the movement of the blast piston and the compression of the quenching gas in the high pressure tank.
 5. A compreSsed gas circuit breaker as in claim 4 wherein the compressor is connected between the low pressure space and the upper portion of the blast cylinder above the blast piston.
 6. A compressed gas circuit breaker as in claim 5 wherein the electro-negative gas used as the quenching gas is sulphur hexafluoride.
 7. A compressed gas circuit breaker as in claim 5 wherein the low pressure space further comprises a nozzle formed from insulating material located in juxtaposition to the movable electrical contact and interconnected to the blast valve by a conduit.
 8. A compressed gas circuit breaker as in claim 5 wherein movement of the electrical contacts and the blast valve is conjunctively controlled by a double acting hydraulic system, connected directly to the blast valve and coupled to the movable contact.
 9. A compressed gas circuit breaker for quenching an electrical arc formed between two electrical breaker contacts upon operation of the breaker, said breaker employing an electro-negative gas as a quenching medium comprising a circuit breaker head mounted on an insulated movable carriage, said head having a quenching chamber therein formed of insulating material, two electrical contacts mounted within said chamber and connected to the electrical circuit, one of said contacts being movable, a nozzle formed of insulating material in juxtaposition to the contacts, a high pressure tank adapted to store the quenching gas at pressures below the liquefaction pressure of the gas at low temperatures, a low pressure space within said head including the quenching chamber, a compressor connected between the low pressure space and the high pressure tank to remove gas at low pressures from the low pressure space and introduce the gas at a higher pressure to the high pressure tank, blast piston means movably mounted in the high pressure tank to compress the high pressure gas to a higher pressure upon operation of the breaker, the piston being operated hydraulically by a second cylinder having an hydraulic piston activated by fluid from an hydraulic accumular, and controlled to operate the blast piston only when the breaker operates, and a blast valve mounted between the high pressure tank and the low pressure space to permit the passage of quenching gas from the high pressure tank to the quenching chamber only when the breaker has operated and the electrical contact is disconnected and the blast piston has compressed the gas to a higher pressure. 